Composite materials containing both titanium carbide and alumina are known to those skilled in the art. Thus, for example, such composites may be made by mixing alumina and titanium carbide and sintering the composite. See, e.g., A. J. Vlasov et al., "Oxide-Carbide Type Ceramic Cutting tools" (in Russian), Nauchn. Tr. Vses Nauchno-Issled Proektn. Inst. Tugopl. Met. Tverd. Splavov. (14) 114 (1973); Ogava et al., "Sintered Ceramic for High Speed Cutting Tools," Japan-Kokai, 7658, 410, May 21, 1976, Abstr.; S. Bellamn, J. Sack, "Cutting Tools, Development and Use" (in German), Werkstatt Ber., 108/5/257 (1975); C. Schultz, F. Holtz, "Machining with Oxide Carbide Ceramics," Carbide J., 9/5/4, (1977); R. G. Behrens et al., "Thermochemical Modeling of Thermite-Type Reactions," Proceedings, DARPA/Army Symposium on Self-Propagating High-Temperature Synthesis (SHS), October, 1985; and W. F. Henshaw et al., "Self-Propagating High-Temperature Synthesis of Ceramics in Vacuum," Ceramic Engineering and Science Proceedings, July-August, 1983, pages 634-645. Each of these publications is hereby incorporated by reference into this specification.
One problem with prior art titanium carbide composites is that they contain substantial amounts of titanium monoxide, which detracts from the mechanical properties of materials made from the composite. The titanium component of the composite generally contains from about 3 to about 12 weight percent of oxygen.
The presence of oxygen in the titanium component will embrittle materials made by sintering the composite and will reduce mechanical properties such as the bending strength, hardness, wear resistance, fracture toughness, and the like. Furthermore, the presence of oxygen in the titanium component reduces the oxidation resistance of the sintered products made from the composite.
The theoretical amount of carbon in titanium carbide is about 20 percent; the closer the carbon content in the titanium carbide is to theoretical, the better the mechanical properties are of materials made from the titanium carbide/alumina composite. Prior art titanium carbide/alumina materials contained a titanium carbide component which contained substantially less than 20 percent of carbon, usually being comprised of from about 5 to about 18 percent of carbon.
The prior art does disclose complicated procedures for increasing the carbon content of the titanium carbide component in which, for example, the component is mixed with carbon black and catalyst and reheated at a temperature of about 2,400 degrees centigrade. See., e.g., G. V. Samsonov and Y. S. Umanskiy's "Tverdyye Soyedineniya Tugoplavkikh Metallov," published by the State Scientific Technical Literature Publishing House (Moscow), 1957, However, this prior art procedure is expensive and time consuming.
It is an object of this invention to provide a relatively inexpensive and simple process for the preparation of a composite material comprised of titanium carbide and alumina in which the titanium carbide component contains at least about 19 percent of carbon. It is another object of this invention to provide a titanium carbide/alumina composite with improved sinterability. It is yet another object of this invention to provide a titanium carbide/alumina composite in which a substantial portion of the titanium carbide material is in whisker form. It is yet another object of this invention to provide a process for preparing a monolith which may be produced from the titanium carbide/alumina composite in a single run. It is yet another object of this invention to prepare a complex composite of titanium carbide/titanium nitride/aluminum oxynitride.